Measuring Calorie Expenditure with a BodyMedia

 know I’ve been M.I.A. for a long time, but I’m back because I have something really interesting to talk about: my BodyMedia!

What’s a BodyMedia?

A BodyMedia is a on-body device that tracks your footsteps, heartrate, sleeping patterns, and daily calorie expenditure, and then uploads them to an online dashboard for you to easily view and track.

It looks like a wristwatch worn on your upper left arm, but in fact it’s a sophisticated device that constantly captures data on your movement, skin temperature, and energy expenditure, then uses this information to determine your caloric burn. It’s more sophisticated than a pedometer or heart rate monitor because neither of those can accurately measure calorie expenditure–this does. Of all the products out there, this is the most accurate, with no guesswork or estimation on your part. You can learn more at the BodyMedia website.

Why Use A BodyMedia?

The BodyMedia produces so much data that I haven’t had time to explore all of it’s potential uses, but for now I’m going to focus on calorie tracking. If you’ve ever tried to lose weight, chances are at some point you’ve thought about calories. Too many people obsess over counting and measuring and tracking every bite of food in order to hit some magic calorie goal without ever stopping to consider whether this is the right amount for their body and weight loss goals. Or they spend hours surfing the web and reading articles and crunching numbers trying to figure out how many calories they just burned at the gym and how many miles they need to run to “burn off” last night’s dinner. Or they get hung up on hitting the right number of “net calories” *cough everyone on tumblr cough*, a concept that is inherently meaningless.

None of this makes sense, and none of this is the right way to think about food, exercise, and weight loss. It doesn’t make sense to pull a calorie goal out of thin air without first considering your calorie expenditure. It doesn’t make sense to meticulously track your exercise calories when they’re really just a rough estimate. And it doesn’t make sense to fixate on the calories you burn in an hour at the gym without thinking about the calories you burn during the other 23.

Calories aren’t just something that you burn off running on the treadmill; they’re units of energy that your body uses constantly to survive. Your body doesn’t just shut off when you’re not formally exercising; it’s burning calories constantly as your working, studying, eating, sleeping, and otherwise going through the motions of daily life. This is why trying to eat back your “exercise calories” to hit 1200 “net calories” is so silly: your body doesn’t differentiate between “exercise calories” and any other calories–all that matters is that your intake is less than your output.

Problem is, how do you know your calorie output? A magazine article can’t tell you. An online calculator can’t tell you. And the computer screen on the elliptical sure as heck can’t tell you. These estimates are a good place to start, and they’re certainly better than pulling a number out of thin air. But if you’re going to let your life revolve around those numbers, then you should at least make sure they’re the right numbers, right?

And that’s where the BodyMedia comes in. It eliminates the calculations and estimations and guesswork by giving you an accurate picture of your daily calorie expenditure. It tells you more about your own body than a doctor, trainer, or one-size-fits-all formula ever could. If your goal is to lose weight, it will enable you to calculate exactly how much you need to eat to reach your weight loss goals, allowing you to avoid sabotaging yourself by eating too much or too little. Moreover, you will be able to see the impact that different exercises, activities, and eating styles have on your body both at the time and throughout the day, helping you to find the lifestyle that is best for YOU.

Why I’m Using A BodyMedia

I get asked this all the time at work when my coworkers or tables see my BodyMedia! Right now I’m just using it to gather data and learn more about my body. I’m not actively trying to lose weight in the sense that I’m tracking or limiting my calorie intake–I’m just curious about my calorie expenditure. Specifically I’m interested in how weight-lifting impacts calorie expenditure in the short-term (how much does it increase calorie burn on a daily basis) as well as the long-term (can it permanently increase your metabolism?) I’m also curious about how much I’m burning at work waiting tables.

My BodyMedia Data

First here’s some background on me: I’m 22 years old, 5’8, and about 150 lbs. For the past month, I’ve been lifting heavy weights for 30-75 minutes 4-5x/week. I also have a very active job waiting tables 30-40 hours/week, and am usually fairly active when I’m not at work (biking, housework, running errands etc). Based on BMR calculations, my BMR should be around 1520 calories, meaning that my calorie expenditure should be about 2600 – 2900 assuming a high activity level. I’d estimate I eat about 3000 calories per day, but that’s just a guess since I don’t currently track calories.

I’ve been wearing the BodyMedia since November 9. Shown below are 17 days worth of data (rounded to nearest 10):

During this 17 period, I burned an average of 3290 calories per day. My calorie expenditure ranged from 2430 to 3860 calories. I expended over 3000 calories on 13 out of the 17 days.

My first reaction was, holy shit, no wonder I’m always hungry! This explains why I eat so much! My second reaction was to wonder about the variance from day to day–that’s almost a 1500 difference between the highest and lowest days!

However, this disparity makes sense if you take into account my activity level, particularly the two biggest factors: lifting weights and working. I’ve reproduced the data below using an “L” to indicate days that I lifted, and “W” to indicate days that I worked.

During this 17 day period, I worked 14 days and lifted 10 days. There were 8 days when I lifted and worked, 6 when I worked but didn’t lift, 2 when I lifted but didn’t work, and 1 when I did neither. I summarized the averages for each category below:

  • Worked and lifted (8 days): 3540
  • Worked but didn’t lift (6 days): 3100
  • Lifted but didn’t work (2 days): 3260
  • Didn’t lift or work (1 day): 2430
  • Overall worked vs didn’t work (14 days/3 days): 3350 vs 2980
  • Overall lifted vs didn’t lift (10 days/7 days): 3490 vs 3000

Conclusions

Right now my conclusions are preliminary because I don’t have much data–I just wanted to share what I had now! However, here’s a few of my thoughts right off the bat:

  1. First off all, I’m burning a LOT of calories. Significantly more than you’d expect based on standardized calculations for my age, size, and activity level. It’s a good reminder that estimations are just that–estimations–and the standard 2000 calories/day doesn’t apply to everyone–if you’re young and active you probably can and should be eating more than that.
  2. Lifting makes a difference. I average almost 500 calories more on days that I lift versus days that I don’t (3490 vs 3000). HOWEVER, this doesn’t mean that I necessarily burned 500 calories during that particular hour of lifting–just that lifting increases overall daily burn (the BodyMedia can show the exact calorie burn during a particular time to prove my point, I just haven’t analyzed it that deeply yet).
  3. Also just because I average 3000 calories per day on my days off from lifting doesn’t mean I’d burn 3000 calories anyway if I’d never picked up a weight. Your metabolism depends on your general pattern of activity, not just your day-to-day activity, and I have a feeling that if I took a month off lifting, my baseline would be much lower. I’m not going to do this on purpose, but it might occur naturally, hence my effort to constantly gather data for comparison purposes.
  4. Activity level matters too: an active lifestyle beats hours of cardio. Over these 17 days I averaged 370 calories more on days that I worked (3350 vs 2980). Moreover, when I look at the breakdown of individual days, I can see a big difference–all the days I hit over 3600 calories were ones I worked long, busy shifts and/or was active outside of work (in addition to lifting). Note that none of this is “formal exercise” but it still burns calories.
  5. My metabolism didn’t used to be this fast. In fact, my whole life I thought I had a pretty slow metabolism, based on the fact that I was overweight as a kid despite having normal eating habits. But I believe that you can increase your metabolism by weight lifting and by EATING, and this supports my belief.
  6. On the other hand, I don’t think I’m eating and expending exponentially more calories than the average person–I just think I’m more aware of it. Most people can and do eat more than they realize, but they aren’t really tracking their intake so they just assume they’re eating the “normal” amount you commonly hear thrown about: 1500, 1800, 2000 etc. When people do track calories it’s usually because they’re trying to lose weight, so that number isn’t going to be representative of an average day. And everyone underestimates.
  7. Based on this you can see why low-calorie diets are often doomed to fail. If Joe Schmo thinks he’s eating about 2000 calories a day, since that’s what the cereal box says (seriously, I’m pretty sure this is where I got my idea of a”normal” amount of calories from), then a 1500-calorie weightloss plan sounds reasonable. But in reality, he’s eating more like 3500 calories a day, he just doesn’t know it. So when he goes on a 1500 calorie doctor-approved diet plan, he feels like he’s starving–because he literally is. After a few days he can’t take it anymore and goes on a fast food binge. Or decides dieting is impossible and gives up altogether. Whereas if he had changed his target to 2500 calories he could having stuck to the diet for much longer, steadily losing 2 lbs/week until he hits his goal.

Stay Tuned…

I need to wrap it up for now, but I’ll be back with more posts as I get more data and delve more deeply into the data I have. I hope this was helpful and feel free to get in touch with any questions; I intend to be more active on here from here on out!

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